Question

Assertion :At low pressure van der Waal's equation is reduced to $[P+\frac{a}{V^2}]V=RT$. Reason: The compressibility factor corresponding to low pressure is given by: $1-\frac{RTV}{a}$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is C Assertion is correct but Reason is incorrect

At low pressures:
V is large and b is negligible in comparison with V.

The Van der Waals equation reduces to:
$(P+\frac{a}{V^2})V=RT$

$PV+\frac{a}{V}=RT$
Also,

$PV+\frac{a}{V}=RT$

So, $PV=RT-\frac{a}{V}$ and $Z=\frac{PV}{RT}=[1-\frac{a}{RTV}]$